1. Field of the Invention
This invention relates in general to an atomizing fuel nozzle with particular application to gas turbines.
2. Description of the Prior Art
The fuel for a gas turbine is normally atomized in an oil nozzle by means of a small orifice which ejects the fuel under pressure into an air stream. The air stream is normally caused to swirl about the outer periphery of the nozzle thus improving the atomizing and mixing of the fuel and air. Because of the difficult conditions under which such jets operate, it is usual for deposits to form within the nozzle caused by material in the air supply and such deposits tend to obstruct the air flow through the nozzle. Also, because the oil supplied to one portion of the nozzle is at one temperature and the air surrounding another portion is at a different temperature, the differential in temperature between the oil and the air will cause the differential temperature of the components of the nozzle.
In a gas turbine in operation, it is normal for the surrounding air to be at high temperature and the fuel to be relatively low temperature therefore, the various parts of the nozzle are subjected to different temperatures and these differential temperatures, which build up during starting and shut-down, cause relative motion between the various components of the nozzle as the temperature differential causes differential expansion of the components. This differential expansion stabilizes at operating temperature with the result that two critical components of the nozzle remain separated until shut-down. The exposure of the separated surfaces to the environment inside the combustor produces pitting of said surfaces which needs must form an airtight seal during each and every start of the gas turbine.